Support, Protection and Movement

An ant carries with ease a flower petal that is heavier than the ant’s
body weight

Of Grasshoppers and Superman
“A dog,” remarked Galileo in the seventeenth century,
“could probably carry two or three such dogs upon his
back; but I believe that a horse could not carry even one of
its own size.” Galileo was referring to the principle of scaling,
a procedure that allows us to understand the consequences
of changing body size. A grasshopper can jump to
a height of 50 times the length of its body, yet a man in a
standing jump cannot clear an obstacle that is no higher
than he is tall. Without an understanding of scaling, this
comparison could easily lead us to the erroneous conclusion
that there is something very special about the musculatures
of insects. To the authors of a nineteenth-century entomology
text it seemed that “This wonderful strength of insects is
doubtless the result of something peculiar in the structure
and arrangement of their muscles, and principally their
extraordinary power of contraction.” But grasshopper muscles
are in fact no more powerful than human muscles
because muscles of small and large animals exert the same force per cross-sectional area. Grasshoppers leap high in
proportion to their size because they are small, not because
they possess extraordinary muscles.

The authors of this nineteenth-century text further suggested
that it was fortunate that higher animals were withheld
the powers of insects, for they would surely have
“caused the early desolation of the world.” More probably,
such powers would have led to their own desolation. For
earthly mortals would need more than superhuman muscles
were they to leap in the proportions of a grasshopper. They
would require superhuman tendons, superhuman ligaments,
and superhuman bones to withstand the stresses of mighty
contractions, not to mention the crushing strains of landing
again on earth at terminal velocity. The feats of Superman
would be quite impossible were he built of the structural
materials available to earthbound animals, rather than of the
wondrous materials available to inhabitants of the mythical
planet Krypton.